With ever increasing concern for public safety and protection of the environment, it has become desirable, if not essential, that leaks in tanks, pipelines or other containers containing material such as hazardous chemicals, petroleum etc., be immediately detected. This would apply to underground tanks or pipelines, which are not accessible or visible, as well as tanks and pipelines above the surface, so that when leakage occurs the immediate safety measures may be taken.
Heretofore, a number of detection systems have been proposed, such as, U.S. Pat. Nos. 3,564,526, granted Feb. 16, 1971 and 3,995,472, granted Dec. 7, 1976. The first of these patents utilizes a pair of insulated conductors adjacent a buried pipeline, with the leaking material causing a degrading of the insulation and thus a short circuit of the conductors, which activates an alarm. Not only does this system require two insulated conductors throughout the length of the sensor, which is expensive, but should a break exist in one of the sensors between the leakage and the monitor, the system would be ineffective. In addition, it may be undesirable in many applications to have a short circuit between conductors amid the leaking material.
The second of these patents utilizes a degradable pneumatic sensor coupled with a monitor. The sensor is pressurized with the leaking material causing the sensor to degrade resulting in a pressure loss which is sensed by the monitor thereby indicating a leak. While this system may have increased application than the first mentioned, it still requires the maintenance of a pneumatically pressurized sensor which is expensive and which may be difficult to effectively maintain, especially in long sensor applications, which may reduce the reliability of the system and increasing the occurrences of false alarm.